The presence of what appears to be a Stronglight 99 crankset suggests it may be a PX60, as opposed to a PX10. I don't think it's a PY10 as the Reynolds decals appear to have green numbering, as opposed to red, and as suggested by Pogue' the rear derailleur appears to be an SX, as opposed to an SLJ.

The decals do suggest 1975 to 1978, but the derailleur suggests it's from the latter end of the range.